I make mind 12 to 24 inch squares. I have a stack of random fabrics and pieces of batting, and before I start on a quilt, I do some warming up on one of these. If the fabric is fairly nice, I'll sometimes turn them into random little "gift" things -- hotpads, pillows, eyeglass cases, doll quilt, baby burp pads.
Sometimes even the plain old muslin, with a very imperfect quilting effort, looks really cool when cut down into something smaller -- an i-pod case, wheelchair armrest cover, basket liner. I just keep the collection of efforts in a corner and pull them out occasionally to use for whatever creative project I've got going.
RST